once upon a time, Adrian wanna buy a Xmas present for Lynette. but he had no money.
so he borrow $50 from Avan and $50 from Victor to buy the $97 present.
after he bought it, he received $3 as a change from the cashier.
so he return $1 to Avan and $1 to Victor.
Therefore he own Avan and Victor $49 each and had only $1 to himself.

but...

49 * 2 = 98
then 98 + 1 = 99

but the sum addup should be $100 so where had the missing $1 gone to??